The charaterization of the multiple forms of monoamine oxidase (MAO) and the nature of the enzyme-membrane interaction are being studied. Three basic techniques are being used to investigate this interaction: (1) immunological studies; (2) C14-substrate catalytic studies; (3) electron spin resonance binding studies. The membrane environment of the enzyme is perturbed using a variety of methods (phospholipases, lipid solvent extraction, lipid ligands) and the effect of this perturbation studied in terms of catalytic activity (tryptamine, phenylethylamine); inhibitor specificity (clorgyline, deprenyl, pargylene); and binding activity (spin labeled hydroxyamphetamine and spin labeled hydroxypargyline. C14-substrate and inhibitory specificites of normal human platelet monoamine oxidase as well as schizophrenic platelet monoamine oxidase are currently being investigated. The developmental characteristics of rat brain monoamine oxidase, using the above-mentioned techniques are being studied.